Add enumeration for first wall and blanket coolant loop types

[chris-ashe]

Description

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[Copilot]

Pull request overview

This PR introduces a named enumeration for the “shared vs separate” first-wall / blanket primary coolant loop configuration and replaces several hard-coded 0/1 comparisons/assignments with the enum values inside the blanket thermal-hydraulic calculations.

Changes:

• Add FWBlktCoolantLoopTypes(IntEnum) for i_fw_blkt_shared_coolant.
• Replace several assignments and conditionals in primary_coolant_properties() and thermo_hydraulic_model() to use the enum members instead of raw integers.

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[Copilot]

FWBlktCoolantLoopTypes(...) will raise ValueError if fwbs_variables.i_fw_blkt_shared_coolant is 2, but the input layer currently allows choices=[0, 1, 2] for this variable (process/core/input.py:1915-1917). This introduces a runtime crash vs the prior numeric comparison logic. Either (a) extend the enum to cover the 2 case (and document what it means), (b) tighten input validation to only allow 0/1, or (c) avoid casting here and compare the raw value to the enum members (since IntEnum already compares equal to int). Consider adding a unit test to cover the non-0/1 path so this can’t regress.

Suggested change

	i_fw_blkt_shared_coolant = FWBlktCoolantLoopTypes(
	fwbs_variables.i_fw_blkt_shared_coolant
	)
	# Compare the raw value directly to the IntEnum member rather than
	# coercing it to FWBlktCoolantLoopTypes. The input layer currently
	# permits values beyond the defined enum members, and IntEnum values
	# compare equal to ints without raising ValueError for those cases.
	i_fw_blkt_shared_coolant = fwbs_variables.i_fw_blkt_shared_coolant

[codecov-commenter]

Codecov Report

❌ Patch coverage is 28.57143% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 52.12%. Comparing base (205f3b6) to head (a2a20cf).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
process/models/blankets/blanket_library.py	28.57%	15 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4210   +/-   ##
=======================================
  Coverage   52.11%   52.12%           
=======================================
  Files         148      148           
  Lines       30406    30411    +5     
=======================================
+ Hits        15847    15852    +5     
  Misses      14559    14559           

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